The invention relates to a technology effective for application to a display driver device for driving a display panel, and a liquid crystal display driver device for driving a liquid crystal panel, and more particularly, to a technology effective for application to a liquid crystal driver (semiconductor integrated circuit for driving liquid crystals) for driving source lines of, for example, a TFT color liquid-crystal panel.
A liquid crystal display, as one of displays, is comprised of a liquid crystal display panel (hereinafter referred to also as a liquid crystal panel) as a display panel, a liquid crystal display controller (liquid crystal controller) as a display controller, a liquid crystal display driver device (liquid crystal driver) as a display driver, for driving the liquid crystal display panel under control by the controller, and so forth. There have thus far been proposed various types of the liquid crystal panels such as a passive type panel, an active-matrix type panel, and so forth.
Among those, a TFT liquid crystal panel, as one of the active-matrix type panels, has a construction in which a plurality of gate lines (scanning lines), and a plurality of source lines (signal lines) are disposed so as to intersect each other, an electrode serving as a pixel, and a transistor for applying a voltage to the electrode are disposed at respective crossover points, and liquid crystals are sandwiched between the respective electrodes, and a common opposite electrode. A source driver sequentially applies a pixel signal to the source lines of the liquid crystal panel, constructed as described, in sync with select actions of the respective gate lines line by line on a time-sharing basis.
As a source driver for driving a large screen TFT liquid crystal panel, use is made of a multi-output liquid crystal driver having a plurality of output terminals. The multi-output liquid crystal driver outputs a drive signal for the liquid crystal panel in sync with a line output signal inputted in order to give timing for impressing a voltage to the respective source lines. With the conventional multi-output liquid crystal driver, all the output terminals outputs the drive signal at the same timing, so that currents for driving the liquid crystal panel are converged, thereby causing a problem that a large current instantaneously flows, and the large current causes a spike-like noise to occur to a power source line and the signal lines, and a power source voltage to drop.
In general, as the radio wave environment becomes more complex, there arises the need for taking into account EMI (electromagnetic interference) of not only electronic equipment alone, but also a system made up of the same. With a liquid crystal display device using the conventional multi-output liquid crystal driver, since the source lines of the liquid crystal panel are concurrently driven, a large current instantaneously flows, and the large current causes a spike-like noise to occur to the power source line and the signal lines, thereby raising the risk of occurrence of EMI. It is necessary to prevent currents for driving the liquid crystal panel from being converged in order to reduce the EMI for one thing.
Accordingly, the inventor et al, have developed the invention relating to the source driver designed so as to deter occurrence of the EMI, wherein a plurality of source outputs are divided into two groups, for example, the right half and left half, to thereby avoid convergence of currents by staggering respective output timings as shown in FIG. 1, and have already submitted the application for the invention (Patent Document 1).
Patent Document 1: JP-A No. 233358/2003